In a reciprocating compressor driven by a linear motor, the gas suction and gas compression operations are performed by the reciprocating axial movements of each piston inside a cylinder, which is closed by a cylinder head and mounted within a hermetic shell, in the cylinder head being positioned the suction and discharge valves that control the admission and discharge of the gas in relation to the cylinder. The piston is driven by an actuating means that supports magnetic components operatively associated with a linear motor affixed to the shell of the compressor.
In some known constructions, each piston-actuating means assembly is connected to a resonant spring affixed to the hermetic shell of the compressor, in order to operate as a guide for the axial displacement of the piston and make the whole assembly act resonantly in a predetermined frequency, allowing the linear motor to be adequately dimensioned to continuously supply energy to the compressor upon operation.
In a known construction, two helical springs are mounted under compression against the actuating means on each of the sides thereof. The piston forms, jointly with the actuating means and with the magnetic component, the resonant assembly of the compressor, which is driven by the linear motor and has the function of developing a reciprocating linear movement, making the movement of the piston inside the cylinder exert a compressive action on the gas admitted through the suction valve, to the point in which said gas can be discharged to the high pressure side through the discharge valve.
Helical springs under compression, regardless of the shape of the last coil that will form the contact region with the piston, generate a contact force with an uneven distribution along a determined circumferential contact extension, with a compressive force concentration in the region where the last coil starts to contact the piston.
In a known solution (U.S. Pat. No. 5,525,845), the coupling between the helical springs and the piston occurs by the provision of a thin cylindrical rod, which is sufficiently laterally flexible to absorb the lateral movements of the springs, but which is axially rigid to transmit the axial force to the piston.
In another known construction, the helical springs are seated on a disc that is connected to the piston, thus applying all the force to the piston. However, the helical springs not only generate the axial force, but also generate radial forces, and the axial force itself is not concentric to the axis of symmetry of the springs. Such spring imperfections force the piston, causing friction and higher energy consumption, which impairs the performance of the linear compressor.